Digital road maps for navigation systems comprise two-dimensional networks of road segments. A three-dimensional map output is desirable for the purpose of better orientation, particularly in the case of a map representation on a large scale.
U.S. Pat. No. 5,757,290 discloses a navigation system which represents a road map from a bird's-eye perspective. The three-dimensional effect is supported by the use of colored variations dependent on distance.
Patent application EP 0 660 290 A1 relates to a three-dimensional representation from a bird's-eye perspective, in which different scales are used for a near zone and a far zone.
Patent application EP 0 752 687 A2 discloses a three-dimensional (3D) representation from a bird's-eye perspective for navigation systems, in the case of which application the transformation of digital road map data into the bird's-eye perspective is optimized by means of conversion tables.
The representation of a road map in the bird's-eye perspective is performed by a perspective projection which is performed from a virtual, elevated viewpoint. The result is to produce a pseudo-3D effect which causes the plane to run together into a vanishing point. Thus, no actual 3D information is used, but the plane is still flat.
Laid Open patent application DE 198 35 874 A1 discloses a map display apparatus which is intended to render possible on a large-area map a direction-independent feeling for distance in conjunction with dynamic compression of the map edges. A lateral transformation in the plane is undertaken for this purpose. A transformation into the third dimension does not take place.
In one embodiment of the invention, there is a method for obtaining a three-dimensional map representation for a navigation system from two-dimensional road map data having a network of road segments. The method includes, for example, obtaining road map data for a field of view that is to be represented and has a predetermined visual range being curved into the third dimension in a radially symmetric fashion about a virtual viewpoint by a polynomial transformation.
In another aspect of the invention, the virtual viewpoint is determined continuously by the navigation system, and the field of view is moved synchronously with the virtual viewpoint.
In another aspect of the invention, objects are placed in the field of view as three-dimensional geometric bodies.
In yet another aspect of the invention, the objects are provided with a texture.
In another aspect of the invention, the vehicle is represented in the field of view.
In another aspect of the invention, the field of view is illuminated as at least one of a function of the time of day and the curvature of the represented sections.
In still another aspect of the invention, a meshed network is displayed.
In another aspect of the invention, route segments of the road map data are provided with boundary lines, and the boundary lines are distorted into a curved course in the region of juxtaposed road segments.
In another embodiment of the invention, there is a navigation system. The system includes, for example, a display device, a position-determining unit, a storage medium on which two-dimensional road map data is stored with the aid of a network of road segments, and a conversion unit to convert two-dimensional road map data from a field of view and has a predetermined visual range into a view curved in the shape of a dish.